Study On The Preparation And Superhydrophobic Property Of Boehmite Films With Special Morphology

In this paper,three-dimensional flower-like boehmite was prepared successfully by a simple hydrothermal method,using Al（NO₃）₃·9H₂O as the aluminum source and sodium acetate as the precipitant.By changing the hydrothermal time and the type of precipitant,the formation mechanism of flower-like boehmite was explored.The formation mechanism of three stages from basic structure unit to middle structure bundle to flower structure is proposed.The first stage was the formation of basic structure unit.It was also regarded as the Oswald ripening process.At the beginning of the hydrothermal reaction,small nanoparticles are formed.In order to reduce the surface free energy,small particles aggregated into larger nanoparticles.This process was known as Oswald ripening.The growth rate of the crystal along all directions was different due to the different surface energy of each surface during small nanoparticles grew into large ones.So it will lead to the formation of basic structure units with different morphologies.The second stage was the directional attachment process of nano-structure units,namely the formation of intermediate structure bundles.It had no obvious time boundary with the first stage.The third stage was self-assembly of the intermediate structure.In the acidic solution,the positively charged boehmite surface will absorb the anions in the solution and form an electron double layer.But at the same time,the surface tension of boehmite would be weaken with the increase of surface acidity.The weakening of the surface tension will cause the boehmites to be close to each other.The electron double layer of the boehmite was compressed,resulting in the weakening of the repulsive force between the structure of the boehmites.Then the hydrogen bond,van der Waals force and electrostatic force between the boehmite molecules kept balance.Finally a stable three-dimensional flower-like structure was formed.Boehmite films with special morphologies and high specific surface area were prepared on glass by one-step hydrothermal method.After hydrophobic treatment of the film samples,boehmite films with super hydrophobicity were obtained.XRD,TG,SEM,Malvern,FTIR,BET,water contact Angle test and other characterization methods were used to systematically investigate the influence of aluminum source concentration,precipitator concentration,hydrothermal time,precipitator type and surfactant on the morphology and superhydrophobic properties of boehmite films.The following conclusions:the super hydrophobic boehmite film samples with regular and abundant surface structure can be obtained with the sodium acetate as precipitant,10 wt.%of Al（NO₃）₃·9H₂O,under hydrothermal temperature 190℃for 12 h without any surfactant...